We investigated the stridulatory courtship initiated by male-male contact after agonistic encounters and the effect of dominance status on subsequent reproductive behavior in the cricket Gryllus bimaculatus. When two male crickets were kept together in a small area, their dominance status was quickly established through fighting or non-fighting interactions. Approximately 10 min after pairing, most dominant males produced calling and/or courtship songs in the presence of subordinate males. This behavior appeared to be triggered by some contact chemicals on the body surface of the males. Stimulation using the forewing of a neutral male induced courtship in dominant males at a higher level compared with neutral males which were not previously paired with males. These observations suggest that the sexual motivation in dominant males increased because of previous agonistic interactions. In contrast, subordinate males remained silent. Stimulation using the male forewing induced stridulation to a lesser degree in subordinate males than in neutral males, suggesting decreased sexual motivation in subordinate males. Furthermore, only 40% of subordinate males exhibited courtship behavior under triadic conditions (dominant male, subordinate male and female) in contrast with 100% in male-female pairs. This result reveals that subordinate males, being less sexually motivated, are continuously suppressed in their courtship by intermittent attacks by the nearby dominant males. In the other triadic condition where the males were allowed to copulate, 65% of the dominant males copulated, while none of the subordinates did. These results suggest that dominant males have a greater chance to copulate and produce offspring.

Cannibalism of pupae by larvae has been documented in many species of insects, but the features of larval cannibalism and pupal defensive mechanisms against larval cannibalism have been largely ignored. Pupae of tenebrionid beetles rotate their abdominal segments in a circular motion in response to the tactile stimulation of appendages, including legs, antennae, maxillary pulps, and wings. When the pupal abdominal rotation responses of Tenebrio molitor and Zophobas atratus were completely blocked by transecting the ventral nerve cord (VNC) of the pupae, the appendages of the paralytic pupae became initial, major targets for attack by larval cannibals. The majority of 20 paralytic pupae was cannibalized by 100 larvae within 6 h, and almost all the pupae were killed within 2–3 days. In contrast, only a few pupae of Z. atratus and several pupae of T. molitor were cannibalized when the VNC was intact. The abdominal rotation response of the pupae thus functions as an effective defense against larval cannibalism.

To investigate genetic diversity of a major histocompatibility complex (MHC) gene in the brown bear (Ursus arctos) population on Hokkaido Island, northern Japan, we cloned and sequenced parts of exon 2 and intron 2 of the MHC class-II DQA gene from 32 brown bears. According to strict criteria for allele identification established by mammalian MHC nomenclature committees, four DQA types (Urar-DQA*01 to Urar-DQA*04) were identified. Of the four, however, Urar-DQA*04 had a 12-bp deletion not detected in a cDNA analysis, indicating that this is a pseudogene at a distinct locus generated by gene duplication. The nucleotide sequences of the other three DQA alleles, which were expressed (because detected from cDNA), were very similar, indicating lower DQA variation in the Hokkaido brown bear population than in other mammals. We attribute this low genetic diversity to (1) some limited effect of possible balancing selection; (2) bottlenecks and inbreeding after migration and isolation of the Hokkaido brown bear population from the Eurasian Continent; (3) a much slower evolutionary rate in DQA than in other MHC genes in the Hokkaido brown bear population.

The migratory fish ayu, Plecoglossus altivelis, has two forms: an amphidromous form found throughout the Japanese islands and a landlocked form found in Lake Biwa. Because Lake Biwa is one of the sources of the Yodo River, which flows into Osaka Bay, it is likely that there has been contact between the two forms within the Yodo River system. To examine the effects of such contact, 573 ayu were collected from the Yodo River system and several other rivers and compared through an extensive investigation of microsatellite genotyping. Multivariate and individual admixture analyses of microsatellite data showed that samples of upstream migrants collected from the Yodo River in May 2003 included many individuals assigned to the amphidromous form, although fish collections in June and July 2003 were primarily composed of individuals of the landlocked form. Samples of drifting larvae, which we considered to be derived from eggs spawned in the Yodo River system, were mostly assigned to the amphidromous form. These results imply that an indigenous population of the amphidromous form exists and reproduces in the Yodo River system. It is likely that upstream migrants of the landlocked Lake Biwa form are supplied annually as well-developed larvae drifting out from Lake Biwa, but contribute very little to the next generation.

The genetic differentiation and speciation of lizards on oceanic islands may be affected by their rate of overwater dispersal. Cryptoblepharus is one of the most geographically widespread scincid lizards throughout the Indo-Pacific and Australian regions. Cryptoblepharus nigropunctatus is the northernmost species of the genus, dwelling on several small Pacific islands. To examine the colonization history of this lizard, mitochondrial 16S rDNA and D-loop sequences were compared among populations of the Ogasawara Islands consisting of four island groups (the Muko-jima, Chichijima, Haha-jima, and Kazan groups), and an isolated island, Minamitori-shima (Marcus Island). These four groups and Minamitori-shima have not been connected to each other because each is surrounded by deep sea (>100 m). DNA analyses showed that the lizard populations on individual islands had each representative haplotypes. The ancestors of C. nigropunctatus probably arrived on the islands from the southern Pacific Ocean via wave dispersal and differentiated to produce the present state. They appear to have dispersed from their origin along two independent pathways: one between Kitaiwo-to (Kazan group) and the Muko-jima and Chichi-jima groups, and the other among the Minamitori-shima, Minamiiwo-to (Kazan group), and Haha-jima groups. Limited long-distance overwater dispersal may be responsible for the genetic structure of the C. nigropunctatus populations on these oceanic islands. However, among the small islands within the same island group, D-loop haplotypes were shared and the local genetic diversity was usually high, suggesting frequent gene flow across the same group of islands.

The population dynamics of Branchiostoma japonicum, formerly known as B. belcheri, were investigated from September 2003 to August 2005 in the intertidal zone at Takehara (Hiroshima Prefecture), Seto Inland Sea, Japan. The intertidal population appeared from spring to autumn and disappeared during winter. A laboratory experiment showed that exposure to temperatures below 1°C for 2 hours resulted in severe mortality. This low temperature corresponds to the minimum temperature in sediments in the study area. This result suggested either that the intertidal population collapses in winter because of low temperature, or that the lancelets escape from the intertidal to the subtidal zone. Throughout the research period, no lancelets smaller than 10 mm in body length were found, indicating that no larvae settled in the intertldal zone. The intertldal population is probably maintained by the influx of individuals from the neighboring subtidal population. The mean annual density of the lancelets was greatest (10.6 individuals/m²) at station 1 nearest the low water mark, and lowest (0.3 Individuals/m²) at station 3 furthest from the low water mark. In summer, the water content of the sediments was remarkably lower at station 3 (20.2%) than at station 1 (25.8%). Another laboratory experiment showed that higher mortality occurred from exposure to sediments with a water content less than 25% for 2 hours, comparable to the water content at station 3, suggesting that the spatial distribution of the lancelets upward in the intertidal is restricted by sediment dryness.

Associated with the age-dependent role change of worker honeybees (Apis mellifera L.) from nurse bees to foragers, some structural and functional changes occur in the hypopharyngeal glands (HPGs): nurse bee HPGs are well developed and synthesize major royal jelly proteins (MRJPs), while forager HPGs shrink and synthesize α-glucosidase, which converts nectar into honey. To identify candidate genes involved in the structural and functional HPG changes associated with the age-dependent role change of worker honeybees, we searched for genes whose expression in the HPGs depends on the role of workers, by using differential display and quantitative reverse transcription-polymerase chain reaction. Here, we newly identified a buffy homolog encoding a Bcl-2-like protein as a gene whose expression, like MRJP, is higher in nurse bees than in foragers, and a matrix metalloproteinase 1 (MMP1) homolog as a gene whose expression, like α-glucosidase, is higher in foragers than in nurse bees, suggesting that both suppression of inhibition of the caspase cascade by buffy and degradation of the extracellular matrix by MMP1 are involved in the functional and structural changes of the HPGs. Furthermore, although both buffy and MMP1 were highly expressed in various tissues other than the HPGs, buffy expression in the other tissues did not differ significantly between nurse bees and foragers, whereas MMP1 expression in midgut was also significantly higher in foragers than in nurse bees, as in the HPGs. These results suggest that in buffy and MMP1, expression is regulated in a tissue-preferential manner according to the age-dependent role change of workers.

Partial sequences of the cytochrome c oxidase subunlt I (COI) gene were determined for six species of the genus Diplosoma (Ascidiacea, Didemnidae) to develop tools for species identification. Because each Diplosoma species has distinctly different COI haplotype(s), the gene sequence seems to be usable for species discrimination in this ascidian genus. The phylogenetic hypothesis supported by the COI data is congruent with the distribution of character states of the retractor muscle. In this paper, we describe a new Diplosoma species harboring symbiotic cyanophytes, found on Miyakojima Island, Ryukyu Archipelago, Japan. Diplosoma aggregatum sp. nov. forms mosaic-like aggregates of small colonies. Although the zooids of D. aggregatum are similar to those of D. virens, these species are differentiated by colony form and COI sequences.

During the course of a survey of fig-associated nematodes in eastern Australia, we discovered an unusual diplogastrid nematode that we describe herein as Teratodiplogaster fignewmani gen. nov., sp. nov. This nematode was isolated as adults and juveniles from the syconia of Ficus racemosa in Queensland and Western Australia. It is presumed to be associated with the agaonid fig wasp, Ceratosolen fusciceps, for dispersion to new phase-B sycones. Teratodiplogaster fignewmani gen. nov., sp. nov. was inferred to be the sister taxon to the genus Parasitodiplogaster based upon molecular phylogeny using nearly full-length sequences of the SSU and D2/D3 LSU ribosomal RNA genes. It is sufficiently distinct in morphology (with many autapomorphies) to justify a new monotypic genus with the hypothesis that further species of Teratodiplogaster gen. nov. will be discovered when sycones from other Ficus from tropical Australasia and possibly Africa are sampled.

A new microhylid, Kalophrynus yongi, is described from the Cameron Highlands of Peninsular Malaysia. Morphologically, the new species differs from all known congeners by having a very stout forelimb with a humeral spine in males. Acoustically, it resembles K. baluensis and K. heterochirus and sharply differs from K. interlineatus, K. pleurostigma, K. palmatissimus, and K. nubicola.